GCMS Notes are detailed notes made by a Canadian immigration/visa officer when s/he assesses applications for TRVs/PRs etc.
Now, there's a section for *Admissibility* in the GCMS Notes.... this section has checks such as Security/Criminality/Organized Crime/Medical, etc.... apart from this, there is one additional check called 'Information Sharing'..... Type: Biographic.... Partner: USA (various details show up in Information Sharing).
If someone has previous US immigrant/non-immigrant history, it will show up in these checks for *Admissibility*. Hence, there can be multiple Information Sharing records/checks for each applicant
Hope this answers your query